Because the ICs’ application frequency and speed become higher and trends of system packaging and device under test request higher reliability, a novel technology combining noncontacting measurement method and reconstructing radiation model was proposed to solve signal deliveries in system packages or PCBs. In this study, a novel noncontacting method for the ICs’ measurements was investigated by the design of loop-type near-field probe and reconstructed the radiation model to substitute the traditional measurement methods, such as using probes and SMA connectors. A near-field probe was used to receive the coupling signal. The assessing circuit modeling could be completed by some synthesized theorems. According to the study’s results, frequency responses of reconstruction model developed by theorems, radiation measurements, and simulated by EM methods were highly curve fitting.
Recently, the markets and applications for advanced semiconductor devices’ packaging and measurement technologies increase expeditiously. The traditional contacting probes have numerous disadvantages, including low mobility, high cost, and high damaged rate. Table
Six package designs for investigating electrical effects.
Probe type | Performance | |||
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Cost | Mobility | Probability of damaging the DUT | Probability of damaging the probe | |
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High | Medium | Medium | Medium |
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High | Medium | High | High |
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High | High | Low | Low |
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Low | Low | High | High |
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Low | High | Extremely low | Extremely low |
Even these contacting probes are usually used for ICs’ measurement; they have many unavoidable disadvantages. First, as mentioned above, the ICs become smaller; the contacting probes or SMA connectors are not easily used for measurements, because the reduction in sizes of the probes and SMA connectors is very difficult. The second issue is that, as the measurements are done without sufficient carefulness, contacting processes will usually damage the expensive probes during DUT’s process, leading to significant expense at all time. Third, because the contacting probes have low mobility and uniform calibration, the measurement will take a long time. Every time the contacting probes are moved to a new measurement position, they will leave the damage or defects after a DUT on the surface of the measured devices. That will increase the ratio of devices’ damage, which will increase the measurements’ cost. For those reasons, many researches have focused on the noncontacting measurement methods to find a low-cost and easily fabricated measurement process.
For that, the non-contacting-probe technologies are designed efficiently with broadband, well reproducibility, well directivity, and low loss coupling, respectively. Thus, the non-contacting-probe technologies can transmit or receive signals between different chips or integrated circuits (ICs) in 3D ICs’ applications, and it is established physical model up to 10 GHz with coupling effect and loop effect to restore the signal radiation. Because the high frequency of 10 GHz is required, the devices’ measurements need to be narrower to keep the measurement data remaining precisely. The area of the noncontacting loop is only about 1.8 mm × 1.8 mm and the size can be reduced by a precise process, making the loop small enough to measure tiny DUTs. When a DUT or the measurement position is changed, the noncontacting probes can be horizontally moved in rapid speed. Because E-field probe is suitably used in far-field’s measurements and H-probe is suitably used in near-field’s measurement, the H-probe is used in this study to investigate the noncontacting measurement technique. Because of having high mobility, the noncontacting probes can measure ICs efficiently, and then the needed cost can be reduced. In this study, the near-field probes were used to receive the coupling signal and the circuit modeling could be completely assessed by some synthesized theorems. The differences compared from the measurement results and numerical analysis could be used to validate the feasibility of signal reconstruction.
Recently, many kinds of non-contacting-probe measurement technologies had been investigated [
When the noncontacting probes are above DUT equipment, as Figure
Schematic diagram of calculated impedance formula [
The design of noncontacting measurement probes with this impedance in formulas (
Information of the noncontacting loop-type probe.
Object | Length | Width | Spacing |
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Feed-line | 1 mm | 0.3 mm | 0.15 mm |
Loop | 1.8 mm | 0.2 mm |
Structure of the CPW loop-type probe.
Structure of the four-layer stacked substrate in this paper.
The measurements for the board samples were formed by stacking the different materials in a four-layer structure. As Figure
Material thickness information.
Copper | Material | |||
---|---|---|---|---|
Layer 1 | Pad | 0.043 mm | Solder mask | 0.053 mm |
Layer 2 | Loop | 0.035 mm | PP glue | 0.15 mm |
Layer 3 | DUT | 0.035 mm | Substrate (FR4) | 0.7 mm |
Layer 4 | GND | 0.043 mm | Plated copper | 0.025 mm |
As the transmission line is revealed in Figure
Transmission line measurement.
Three-dimensional stacked structure for 5.3 G filter’s measurement.
Noncontacting measurement model.
In order to obtain the parameters of the modeling structure, formulas (
Parameters of the noncontacting measurement model (DUT: transmission line).
Resistance |
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18 mΩ |
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6.8 kΩ | |
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Capacitance |
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0.42 pF |
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0.07 pF | |
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Inductance |
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5.8137 nH |
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2.5 nH |
Parameters of the noncontacting measurement model (DUT: three-dimensional stacked for 5.3 G filter).
Resistance |
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18 mΩ |
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4.9 kΩ | |
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Capacitance |
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0.42 pF |
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0.06094 pF | |
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Inductance |
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5.8137 nH |
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2.5 nH |
Probe parameters calculation. (a) Resistance and (b) capacitance.
However, the self-inductance
Parameters between loop and DUT calculation. (a) Mutual inductance and (b) dielectric capacitance.
Therefore, the signals in noncontacting probe are obtained by the coupling method, which is different from traditional measurement method by using probes’ contacting process. For that, a complete reduction theory to compensate the being coupled signals measured by the noncontacting probes is needed. The reduction theory for the noncontact probe not only restores the characteristics of the DUT but also creates the similar data with those of the traditional contacting probes. As shown in Figure
Noncontacting measurement model. (a) Equivalent model with lumped component. (b) Equivalent model with alphabet replaced.
If we set point 2 in Figure
Two-port traditional contacting measurement model.
As we substitute
From the return loss and the insertion loss of the restoring theory, the comparisons of model simulation by agilent advanced design system (ADS) and the 3D EM simulation by the analyzing results of high frequency structure simulator (HFSS), the actual measurement values of DUT can completely be obtained. The two ports of noncontacting probe were used to measure the DUT and transmission line and the results are shown in Figure
Figures
Results of transmission line reconstruction. (a) Return loss. (b) Insertion loss.
Results of filter reconstruction. (a) Return loss. (b) Insertion loss.
In this study, a novel noncontact measurement method with the development of using loop-type near-filed probe had been investigated; the transmission lines’ frequency responses were measured by this loop-type probe. Another, a radiation model to reconstruct transmission signals had been delivered by equivalent capacitances, inductances, and resistances extracting, too. All parameter formulas in radiation model had been provided and presented. The comparisons of the performance responses among measurement, radiation model, and electromagnetic simulation tool were fitting. We had shown that the measurement method and radiation model presented in this study were useful to evaluate circuit signal performance and EMI/EMS design, like POP, SiP, and subsystem PCB.
The authors declare that there is no conflict of interests regarding the publication of this paper.